Predictive Reasoning for Controlling Speed of a Vehicle

ABSTRACT

Methods and systems for predictive reasoning for controlling speed of a vehicle are described. A computing device may be configured to identify a first and second vehicle travelling ahead of an autonomous vehicle and in a same lane as the autonomous vehicle. The computing device may also be configured to determine a first buffer distance behind the first vehicle at which the autonomous vehicle will substantially reach a speed of the first vehicle and a second buffer distance behind the second vehicle at which the first vehicle will substantially reach a speed of the second vehicle. The computing device may further be configured to determine a distance at which to adjust a speed of the autonomous vehicle based on the first and second buffer distances and the speed of the autonomous vehicle, and then provide instructions to adjust the speed of the autonomous vehicle based on the distance.

BACKGROUND

Autonomous vehicles use various computing systems to aid in transportingpassengers from one location to another. Some autonomous vehicles mayrequire some initial input or continuous input from an operator, such asa pilot, driver, or passenger. Other systems, for example autopilotsystems, may be used only when the system has been engaged, whichpermits the operator to switch from a manual mode (where the operatorexercises a high degree of control over the movement of the vehicle) toan autonomous mode (where the vehicle essentially drives itself) tomodes that lie somewhere in between.

SUMMARY

The present application discloses embodiments that relate to predictivereasoning for controlling speed of a vehicle. In one aspect, the presentapplication describes a method. The method may comprise identifying afirst vehicle travelling ahead of an autonomous vehicle. The method mayalso comprise identifying a second vehicle ahead of the first vehicle,the first and second vehicles travelling in substantially a same lane asthe autonomous vehicle. The method may also comprise determining a firstbuffer distance, the first buffer distance being a minimal distancebehind the first vehicle at which the autonomous vehicle willsubstantially reach a speed of the first vehicle. The method may alsocomprise determining a second buffer distance, the second bufferdistance being a minimal distance behind the second vehicle at which thefirst vehicle will substantially reach a speed of the second vehicle.The method may also comprise determining a distance at which to adjust aspeed of the autonomous vehicle based on the first and second bufferdistances and the speed of the autonomous vehicle. The method mayfurther comprise providing instructions by a computing device to adjustthe speed of the autonomous vehicle based on the distance.

In another aspect, the present application describes a non-transitorycomputer readable medium having stored thereon executable instructionsthat, upon execution by a computing device, cause the computing deviceto perform functions. The functions may comprise identifying a firstvehicle travelling ahead of an autonomous vehicle. The functions mayalso comprise identifying a second vehicle ahead of the first vehicle,the first and second vehicles travelling in substantially a same lane asthe autonomous vehicle. The functions may also comprise determining afirst buffer distance, the first buffer distance being a minimaldistance behind the first vehicle at which the autonomous vehicle willsubstantially reach a speed of the first vehicle. The functions may alsocomprise determining a second buffer distance, the second bufferdistance being a minimal distance behind the second vehicle at which thefirst vehicle will substantially reach a speed of the second vehicle.The functions may also comprise determining a distance at which toadjust a speed of the autonomous vehicle based on the first and secondbuffer distances and the speed of the autonomous vehicle. The functionsmay further comprise providing instructions to adjust the speed of theautonomous vehicle based on the distance.

In still another aspect, the present application describes a system. Thesystem may comprise at least one processor. The system also may comprisea memory having stored thereon instructions that, upon execution by theat least one processor, cause the system to perform functions. Thefunctions may comprise identifying a first object ahead of an autonomousvehicle. The functions may also comprise identifying a second objectahead of the first object, where the first and second objects are insubstantially a same lane as the autonomous vehicle. The functions mayalso comprise determining a first buffer distance, the first bufferdistance being a minimal distance behind the first object at which theautonomous vehicle will substantially reach a speed of the first object.The functions may also comprise determining a second buffer distance,the second buffer distance being a minimal distance behind the secondobject at which the first object will substantially reach a speed of thesecond object. The functions may also comprise determining a distance atwhich to adjust a speed of the autonomous vehicle based on the first andsecond buffer distances and the speed of the autonomous vehicle. Thefunctions may further comprise providing instructions to adjust thespeed of the autonomous vehicle based on the distance.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the figures and the followingdetailed description.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a simplified block diagram of an example automobile.

FIG. 2 illustrates an example automobile.

FIG. 3 is a flow chart of an example method for adjusting a speed of anautonomous vehicle.

FIG. 4A illustrates an example for determining a distance at which toadjust the speed of the autonomous vehicle.

FIG. 4B illustrates an example for determining a distance at which toadjust the speed of the autonomous vehicle when a traffic control objectis present.

FIG. 5 illustrates an implementation of the example method on a road oftravel.

FIG. 6 is a schematic illustrating a conceptual partial view of acomputer program.

DETAILED DESCRIPTION

The following detailed description describes various features andfunctions of the disclosed systems and methods with reference to theaccompanying figures. In the figures, similar symbols identify similarcomponents, unless context dictates otherwise. The illustrative systemand method embodiments described herein are not meant to be limiting. Itmay be readily understood that certain aspects of the disclosed systemsand methods can be arranged and combined in a wide variety of differentconfigurations, all of which are contemplated herein.

An autonomous vehicle operating on a road or path of travel may beconfigured to identify objects within an environment of the autonomousvehicle in order to determine an adjustment to the autonomous vehicle'scurrent speed. The objects can be other vehicles, traffic controlobjects, or other types of objects. In some examples, each identifiedobject may be considered independently, and the respectivecharacteristics of the object, such as its current speed, acceleration,and range to the vehicle, may be used to determine a speed for theautonomous vehicle to adjust to.

However, in other examples, the autonomous vehicle, or computing deviceassociated with the autonomous vehicle, may be configured to predictbehaviors of the identified objects based on the characteristics of theobjects and a state of the surrounding environment (e.g., traffic, rain,ice on the road, etc.), and the objects may all be consideredtogether—each dependent on each other's behavior. The autonomous vehiclecan then adjust its speed based on the predicted behaviors of theobjects. In other words, the autonomous vehicle can determine whatsteady state the vehicle will need to adjust to (e.g., speed up, slowdown, or stop) based on the predicted behaviors of the objects. Othercharacteristics/factors may be considered as well in order to determinethe speed of the autonomous vehicle, such as a lateral position of theautonomous vehicle in a road/lane of travel, curvature of the road,proximity of static and dynamic objects, etc.

In one example of predictive speed control, a computing device,configured to adjust the speed of an autonomous vehicle, may identifymultiple objects ahead of the vehicle. The objects may include, forexample, other vehicles travelling ahead of the autonomous vehicle inthe same lane as the autonomous vehicle, such as trucks, bicycles, andmotorcycles. The objects may also include other types of static ordynamic objects, such as pedestrians, stop signs, a toll booth, trees,guard rails, etc. Upon identifying the objects, the computing device maybe configured to estimate characteristics of each object, such as theobject's speed, acceleration, size, weight, direction of travel, andlongitudinal and lateral speeds.

After identifying the objects, the computing device may determine abuffer distance for each object between the autonomous vehicle and thefarthest identified object from the autonomous vehicle. For example, ifthe computing device identifies a first and second object ahead of thevehicle, the second object being at a greater distance from theautonomous vehicle than the first object, the computing device maydetermine a first buffer distance at which the autonomous vehicle willsubstantially reach a speed of the first object, and also determine asecond buffer distance at which the first object will substantiallyreach a speed of the second object. The buffer distances may be based onthe speeds of the identified objects. In some examples, the bufferdistances may also be based on other characteristics of the identifiedobjects.

Based on the buffer distances and the speed of the autonomous vehicle,the computing device may then determine a distance at which to adjustthe speed of the autonomous vehicle. The distance may also be a functionof other characteristics of the objects and the autonomous vehicle, aswell as any predetermined (e.g., calibrated) constants. The computingdevice may be configured to then provide instructions to adjust thespeed of the autonomous vehicle based on the distance.

In some embodiments, the instructions may be provided prior to thecomputing device detecting a change of the speed of at least one of theobjects ahead of the autonomous vehicle. As such, the autonomous vehiclemay adjust its speed based on an estimation of the change of the speedof at least one of the objects prior to such change occurring. Such achange in the speed of the object(s) may be evaluated differently invarious embodiments. For example, the change in the speed may beindicated by the speed of the object(s) exceeding a given threshold.Other examples are also possible.

In addition to providing instructions to adjust the speed of theautonomous vehicle, the computing device may be configured to provideinstructions to modify a steering angle of the autonomous vehicle so asto cause the autonomous vehicle to follow a given trajectory and/ormaintain safe lateral and longitudinal distances with the objects in thevicinity of the autonomous vehicle (e.g., cars in adjacent lanes on aroad). The computing device may also be configured to implementheuristics to mimic human-like behavior to determine the distance andadjust the speed of the autonomous vehicle accordingly (and possiblycontrol the autonomous vehicle in other manners, such as adjusting theautonomous vehicle's steering/trajectory).

An example vehicle control system may be implemented in or may take theform of an automobile. Alternatively, a vehicle control system may beimplemented in or take the form of other vehicles, such as cars, trucks,motorcycles, buses, boats, airplanes, helicopters, lawn mowers,recreational vehicles, amusement park vehicles, farm equipment,construction equipment, trams, golf carts, trains, and trolleys. Othervehicles are possible as well.

Further, an example system may take the form of a non-transitorycomputer-readable medium, which has program instructions stored thereonthat are executable by at least one processor to provide thefunctionality described herein. An example system may also take the formof an automobile or a subsystem of an automobile that includes such anon-transitory computer-readable medium having such program instructionsstored thereon.

Referring now to the Figures, FIG. 1 is a simplified block diagram of anexample automobile 100, in accordance with an example embodiment.Components coupled to or included in the automobile 100 may include apropulsion system 102, a sensor system 104, a control system 106,peripherals 108, a power supply 110, a computing device 111, and a userinterface 112. The computing device 111 may include a processor 113, anda memory 114. The computing device 111 may be a controller, or part ofthe controller, of the automobile 100. The memory 114 may includeinstructions 115 executable by the processor 113, and may also store mapdata 116. Components of the automobile 100 may be configured to work inan interconnected fashion with each other and/or with other componentscoupled to respective systems. For example, the power supply 110 mayprovide power to all the components of the automobile 100. The computingdevice 111 may be configured to receive information from and control thepropulsion system 102, the sensor system 104, the control system 106,and the peripherals 108. The computing device 111 may be configured togenerate a display of images on and receive inputs from the userinterface 112.

In other examples, the automobile 100 may include more, fewer, ordifferent systems, and each system may include more, fewer, or differentcomponents. Additionally, the systems and components shown may becombined or divided in any number of ways.

The propulsion system 102 may be configured to provide powered motionfor the automobile 100. As shown, the propulsion system 102 includes anengine/motor 118, an energy source 120, a transmission 122, andwheels/tires 124.

The engine/motor 118 may be or include any combination of an internalcombustion engine, an electric motor, a steam engine, and a Stirlingengine. Other motors and engines are possible as well. In some examples,the propulsion system 102 could include multiple types of engines and/ormotors. For instance, a gas-electric hybrid car could include a gasolineengine and an electric motor. Other examples are possible.

The energy source 120 may be a source of energy that powers theengine/motor 118 in full or in part. That is, the engine/motor 118 maybe configured to convert the energy source 120 into mechanical energy.Examples of energy sources 120 include gasoline, diesel, otherpetroleum-based fuels, propane, other compressed gas-based fuels,ethanol, solar panels, batteries, and other sources of electrical power.The energy source(s) 120 could additionally or alternatively include anycombination of fuel tanks, batteries, capacitors, and/or flywheels. Insome examples, the energy source 120 may provide energy for othersystems of the automobile 100 as well.

The transmission 122 may be configured to transmit mechanical power fromthe engine/motor 118 to the wheels/tires 124. To this end, thetransmission 122 may include a gearbox, clutch, differential, driveshafts, and/or other elements. In examples where the transmission 122includes drive shafts, the drive shafts could include one or more axlesthat are configured to be coupled to the wheels/tires 124.

The wheels/tires 124 of automobile 100 could be configured in variousformats, including a unicycle, bicycle/motorcycle, tricycle, orcar/truck four-wheel format. Other wheel/tire formats are possible aswell, such as those including six or more wheels. The wheels/tires 124of automobile 100 may be configured to rotate differentially withrespect to other wheels/tires 124. In some examples, the wheels/tires124 may include at least one wheel that is fixedly attached to thetransmission 122 and at least one tire coupled to a rim of the wheelthat could make contact with the driving surface. The wheels/tires 124may include any combination of metal and rubber, or combination of othermaterials.

The propulsion system 102 may additionally or alternatively includecomponents other than those shown.

The sensor system 104 may include a number of sensors configured tosense information about an environment in which the automobile 100 islocated. As shown, the sensors of the sensor system include a GlobalPositioning System (GPS) module 126, an inertial measurement unit (IMU)128, a radio detection and ranging (RADAR) unit 130, a laser rangefinderand/or light detection and ranging (LIDAR) unit 132, a camera 134, andactuators 136 configured to modify a position and/or orientation of thesensors. The sensor system 104 may include additional sensors as well,including, for example, sensors that monitor internal systems of theautomobile 100 (e.g., an O₂ monitor, a fuel gauge, an engine oiltemperature, etc.). Other sensors are possible as well.

The GPS module 126 may be any sensor configured to estimate a geographiclocation of the automobile 100. To this end, the GPS module 126 mayinclude a transceiver configured to estimate a position of theautomobile 100 with respect to the Earth, based on satellite-basedpositioning data. In an example, the computing device 111 may beconfigured to use the GPS module 126 in combination with the map data116 to estimate a location of a lane boundary on road on which theautomobile 100 may be travelling on. The GPS module 126 may take otherforms as well.

The IMU 128 may be any combination of sensors configured to senseposition and orientation changes of the automobile 100 based on inertialacceleration. In some examples, the combination of sensors may include,for example, accelerometers and gyroscopes. Other combinations ofsensors are possible as well.

The RADAR unit 130 may be considered as an object detection system thatmay be configured to use radio waves to determine characteristics of theobject such as range, altitude, direction, or speed of the object. TheRADAR unit 130 may be configured to transmit pulses of radio waves ormicrowaves that may bounce off any object in a path of the waves. Theobject may return a part of energy of the waves to a receiver (e.g.,dish or antenna), which may be part of the RADAR unit 130 as well. TheRADAR unit 130 also may be configured to perform digital signalprocessing of received signals (bouncing off the object) and may beconfigured to identify the object.

Other systems similar to RADAR have been used in other parts of theelectromagnetic spectrum. One example is LIDAR (light detection andranging), which may be configured to use visible light from lasersrather than radio waves.

The LIDAR unit 132 may include a sensor configured to sense or detectobjects in an environment in which the automobile 100 is located usinglight. Generally, LIDAR is an optical remote sensing technology that canmeasure distance to, or other properties of, a target by illuminatingthe target with light. As an example, the LIDAR unit 132 may include alaser source and/or laser scanner configured to emit laser pulses and adetector configured to receive reflections of the laser pulses. Forexample, the LIDAR unit 132 may include a laser range finder reflectedby a rotating mirror, and the laser is scanned around a scene beingdigitized, in one or two dimensions, gathering distance measurements atspecified angle intervals. In examples, the LIDAR unit 132 may includecomponents such as light (e.g., laser) source, scanner and optics,photo-detector and receiver electronics, and position and navigationsystem.

In an example, the LIDAR unit 132 may be configured to use ultraviolet(UV), visible, or infrared light to image objects and can be used with awide range of targets, including non-metallic objects. In one example, anarrow laser beam can be used to map physical features of an object withhigh resolution.

In examples, wavelengths in a range from about 10 micrometers (infrared)to about 250 nm (UV) could be used. Typically light is reflected viabackscattering. Different types of scattering are used for differentLIDAR applications, such as Rayleigh scattering, Mie scattering andRaman scattering, as well as fluorescence. Based on different kinds ofbackscattering, LIDAR can be accordingly called Rayleigh LIDAR, MieLIDAR, Raman LIDAR and Na/Fe/K Fluorescence LIDAR, as examples. Suitablecombinations of wavelengths can allow for remote mapping of objects bylooking for wavelength-dependent changes in intensity of reflectedsignals, for example.

Three-dimensional (3D) imaging can be achieved using both scanning andnon-scanning LIDAR systems. “3D gated viewing laser radar” is an exampleof a non-scanning laser ranging system that applies a pulsed laser and afast gated camera. Imaging LIDAR can also be performed using an array ofhigh speed detectors and a modulation sensitive detectors arraytypically built on single chips using CMOS (complementarymetal-oxide-semiconductor) and hybrid CMOS/CCD (charge-coupled device)fabrication techniques. In these devices, each pixel may be processedlocally by demodulation or gating at high speed such that the array canbe processed to represent an image from a camera. Using this technique,many thousands of pixels may be acquired simultaneously to create a 3Dpoint cloud representing an object or scene being detected by the LIDARunit 132.

A point cloud may include a set of vertices in a 3D coordinate system.These vertices may be defined by X, Y, and Z coordinates, for example,and may represent an external surface of an object. The LIDAR unit 132may be configured to create the point cloud by measuring a large numberof points on the surface of the object, and may output the point cloudas a data file. As the result of a 3D scanning process of the object bythe LIDAR unit 132, the point cloud can be used to identify andvisualize the object.

In one example, the point cloud can be directly rendered to visualizethe object. In another example, the point cloud may be converted topolygon or triangle mesh models through a process that may be referredto as surface reconstruction. Example techniques for converting a pointcloud to a 3D surface may include Delaunay triangulation, alpha shapes,and ball pivoting. These techniques include building a network oftriangles over existing vertices of the point cloud. Other exampletechniques may include converting the point cloud into a volumetricdistance field and reconstructing an implicit surface so defined througha marching cubes algorithm.

The camera 134 may be any camera (e.g., a still camera, a video camera,etc.) configured to capture images of the environment in which theautomobile 100 is located. To this end, the camera may be configured todetect visible light, or may be configured to detect light from otherportions of the spectrum, such as infrared or ultraviolet light. Othertypes of cameras are possible as well. The camera 134 may be atwo-dimensional detector, or may have a three-dimensional spatial range.In some examples, the camera 134 may be, for example, a range detectorconfigured to generate a two-dimensional image indicating a distancefrom the camera 134 to a number of points in the environment. To thisend, the camera 134 may use one or more range detecting techniques. Forexample, the camera 134 may be configured to use a structured lighttechnique in which the automobile 100 illuminates an object in theenvironment with a predetermined light pattern, such as a grid orcheckerboard pattern and uses the camera 134 to detect a reflection ofthe predetermined light pattern off the object. Based on distortions inthe reflected light pattern, the automobile 100 may be configured todetermine the distance to the points on the object. The predeterminedlight pattern may comprise infrared light, or light of anotherwavelength.

The actuators 136 may, for example, be configured to modify a positionand/or orientation of the sensors.

The sensor system 104 may additionally or alternatively includecomponents other than those shown.

The control system 106 may be configured to control operation of theautomobile 100 and its components. To this end, the control system 106may include a steering unit 138, a throttle 140, a brake unit 142, asensor fusion algorithm 144, a computer vision system 146, a navigationor pathing system 148, and an obstacle avoidance system 150.

The steering unit 138 may be any combination of mechanisms configured toadjust the heading or direction of the automobile 100.

The throttle 140 may be any combination of mechanisms configured tocontrol the operating speed and acceleration of the engine/motor 118and, in turn, the speed and acceleration of the automobile 100.

The brake unit 142 may be any combination of mechanisms configured todecelerate the automobile 100. For example, the brake unit 142 may usefriction to slow the wheels/tires 124. As another example, the brakeunit 142 may be configured to be regenerative and convert the kineticenergy of the wheels/tires 124 to electric current. The brake unit 142may take other forms as well.

The sensor fusion algorithm 144 may include an algorithm (or a computerprogram product storing an algorithm) executable by the computing device111, for example. The sensor fusion algorithm 144 may be configured toaccept data from the sensor system 104 as an input. The data mayinclude, for example, data representing information sensed at thesensors of the sensor system 104. The sensor fusion algorithm 144 mayinclude, for example, a Kalman filter, a Bayesian network, or anotheralgorithm. The sensor fusion algorithm 144 further may be configured toprovide various assessments based on the data from the sensor system104, including, for example, evaluations of individual objects and/orfeatures in the environment in which the automobile 100 is located,evaluations of particular situations, and/or evaluations of possibleimpacts based on particular situations. Other assessments are possibleas well

The computer vision system 146 may be any system configured to processand analyze images captured by the camera 134 in order to identifyobjects and/or features in the environment in which the automobile 100is located, including, for example, lane information, traffic signalsand obstacles. To this end, the computer vision system 146 may use anobject recognition algorithm, a Structure from Motion (SFM) algorithm,video tracking, or other computer vision techniques. In some examples,the computer vision system 146 may additionally be configured to map theenvironment, track objects, estimate speed of objects, etc.

The navigation and pathing system 148 may be any system configured todetermine a driving path for the automobile 100. The navigation andpathing system 148 may additionally be configured to update the drivingpath dynamically while the automobile 100 is in operation. In someexamples, the navigation and pathing system 148 may be configured toincorporate data from the sensor fusion algorithm 144, the GPS module126, and one or more predetermined maps so as to determine the drivingpath for the automobile 100.

The obstacle avoidance system 150 may be any system configured toidentify, evaluate, and avoid or otherwise negotiate obstacles in theenvironment in which the automobile 100 is located.

The control system 106 may additionally or alternatively includecomponents other than those shown.

Peripherals 108 may be configured to allow the automobile 100 tointeract with external sensors, other automobiles, and/or a user. Tothis end, the peripherals 108 may include, for example, a wirelesscommunication system 152, a touchscreen 154, a microphone 156, and/or aspeaker 158.

The wireless communication system 152 may be any system configured to bewirelessly coupled to one or more other automobiles, sensors, or otherentities, either directly or via a communication network. To this end,the wireless communication system 152 may include an antenna and achipset for communicating with the other automobiles, sensors, or otherentities either directly or over an air interface. The chipset orwireless communication system 152 in general may be arranged tocommunicate according to one or more other types of wirelesscommunication (e.g., protocols) such as Bluetooth, communicationprotocols described in IEEE 802.11 (including any IEEE 802.11revisions), cellular technology (such as GSM, CDMA, UMTS, EV-DO, WiMAX,or LTE), Zigbee, dedicated short range communications (DSRC), and radiofrequency identification (RFID) communications, among otherpossibilities. The wireless communication system 152 may take otherforms as well.

The touchscreen 154 may be used by a user to input commands to theautomobile 100. To this end, the touchscreen 154 may be configured tosense at least one of a position and a movement of a user's finger viacapacitive sensing, resistance sensing, or a surface acoustic waveprocess, among other possibilities. The touchscreen 154 may be capableof sensing finger movement in a direction parallel or planar to thetouchscreen surface, in a direction normal to the touchscreen surface,or both, and may also be capable of sensing a level of pressure appliedto the touchscreen surface. The touchscreen 154 may be formed of one ormore translucent or transparent insulating layers and one or moretranslucent or transparent conducting layers. The touchscreen 154 maytake other forms as well.

The microphone 156 may be configured to receive audio (e.g., a voicecommand or other audio input) from a user of the automobile 100.Similarly, the speakers 158 may be configured to output audio to theuser of the automobile 100.

The peripherals 108 may additionally or alternatively include componentsother than those shown.

The power supply 110 may be configured to provide power to some or allof the components of the automobile 100. To this end, the power supply110 may include, for example, a rechargeable lithium-ion or lead-acidbattery. In some examples, one or more banks of batteries could beconfigured to provide electrical power. Other power supply materials andconfigurations are possible as well. In some examples, the power supply110 and energy source 120 may be implemented together, as in someall-electric cars.

The processor 113 included in the computing device 111 may comprise oneor more general-purpose processors and/or one or more special-purposeprocessors (e.g., image processor, digital signal processor, etc.). Tothe extent that the processor 113 includes more than one processor, suchprocessors could work separately or in combination. The computing device111 may be configured to control functions of the automobile 100 basedon input received through the user interface 112, for example.

The memory 114, in turn, may comprise one or more volatile and/or one ormore non-volatile storage components, such as optical, magnetic, and/ororganic storage, and the memory 114 may be integrated in whole or inpart with the processor 113. The memory 114 may contain the instructions115 (e.g., program logic) executable by the processor 113 to executevarious automobile functions, including any of the functions or methodsdescribed herein.

The components of the automobile 100 could be configured to work in aninterconnected fashion with other components within and/or outside theirrespective systems. To this end, the components and systems of theautomobile 100 may be communicatively linked together by a system bus,network, and/or other connection mechanism (not shown).

Further, while each of the components and systems is shown to beintegrated in the automobile 100, in some examples, one or morecomponents or systems may be removably mounted on or otherwise connected(mechanically or electrically) to the automobile 100 using wired orwireless connections.

The automobile 100 may include one or more elements in addition to orinstead of those shown. For example, the automobile 100 may include oneor more additional interfaces and/or power supplies. Other additionalcomponents are possible as well. In these examples, the memory 114 mayfurther include instructions executable by the processor 113 to controland/or communicate with the additional components.

FIG. 2 illustrates an example automobile 200, in accordance with anembodiment. In particular, FIG. 2 shows a Right Side View, Front View,Back View, and Top View of the automobile 200. Although automobile 200is illustrated in FIG. 2 as a car, other examples are possible. Forinstance, the automobile 200 could represent a truck, a van, asemi-trailer truck, a motorcycle, a golf cart, an off-road vehicle, or afarm vehicle, among other examples. As shown, the automobile 200includes a first sensor unit 202, a second sensor unit 204, a thirdsensor unit 206, a wireless communication system 208, and a camera 210.

Each of the first, second, and third sensor units 202-206 may includeany combination of global positioning system sensors, inertialmeasurement units, RADAR units, LIDAR units, cameras, lane detectionsensors, and acoustic sensors. Other types of sensors are possible aswell.

While the first, second, and third sensor units 202 are shown to bemounted in particular locations on the automobile 200, in some examplesthe sensor unit 202 may be mounted elsewhere on the automobile 200,either inside or outside the automobile 200. Further, while only threesensor units are shown, in some examples more or fewer sensor units maybe included in the automobile 200.

In some examples, one or more of the first, second, and third sensorunits 202-206 may include one or more movable mounts on which thesensors may be movably mounted. The movable mount may include, forexample, a rotating platform. Sensors mounted on the rotating platformcould be rotated so that the sensors may obtain information from eachdirection around the automobile 200. Alternatively or additionally, themovable mount may include a tilting platform. Sensors mounted on thetilting platform could be tilted within a particular range of anglesand/or azimuths so that the sensors may obtain information from avariety of angles. The movable mount may take other forms as well.

Further, in some examples, one or more of the first, second, and thirdsensor units 202-206 may include one or more actuators configured toadjust the position and/or orientation of sensors in the sensor unit bymoving the sensors and/or movable mounts. Example actuators includemotors, pneumatic actuators, hydraulic pistons, relays, solenoids, andpiezoelectric actuators. Other actuators are possible as well.

The wireless communication system 208 may be any system configured towirelessly couple to one or more other automobiles, sensors, or otherentities, either directly or via a communication network as describedabove with respect to the wireless communication system 152 in FIG. 1.While the wireless communication system 208 is shown to be positioned ona roof of the automobile 200, in other examples the wirelesscommunication system 208 could be located, fully or in part, elsewhere.

The camera 210 may be any camera (e.g., a still camera, a video camera,etc.) configured to capture images of the environment in which theautomobile 200 is located. To this end, the camera 210 may take any ofthe forms described above with respect to the camera 134 in FIG. 1.While the camera 210 is shown to be mounted inside a front windshield ofthe automobile 200, in other examples the camera 210 may be mountedelsewhere on the automobile 200, either inside or outside the automobile200.

The automobile 200 may include one or more other components in additionto or instead of those shown.

A control system of the automobile 200 may be configured to control theautomobile 200 in accordance with a control strategy from among multiplepossible control strategies. The control system may be configured toreceive information from sensors coupled to the automobile 200 (on oroff the automobile 200), modify the control strategy (and an associateddriving behavior) based on the information, and control the automobile200 in accordance with the modified control strategy. The control systemfurther may be configured to monitor the information received from thesensors, and continuously evaluate driving conditions; and also may beconfigured to modify the control strategy and driving behavior based onchanges in the driving conditions.

FIG. 3 is a flow chart of an example method 300 for adjusting a speed ofa vehicle. The method 300 may include one or more operations, functions,or actions as illustrated by one or more of blocks 302-308. Although theblocks are illustrated in a sequential order, these blocks may in someinstances be performed in parallel, and/or in a different order thanthose described herein. Also, the various blocks may be combined intofewer blocks, divided into additional blocks, and/or removed based uponthe desired implementation.

In addition, for the method 300 and other processes and methodsdisclosed herein, the flowchart shows functionality and operation of onepossible implementation of present embodiments. In this regard, eachblock may represent a module, a segment, or a portion of program code,which includes one or more instructions executable by a processor forimplementing specific logical functions or steps in the process. Theprogram code may be stored on any type of computer readable medium ormemory, for example, such as a storage device including a disk or harddrive. The computer readable medium may include a non-transitorycomputer readable medium, for example, such as computer-readable mediathat stores data for short periods of time like register memory,processor cache and Random Access Memory (RAM). The computer readablemedium may also include non-transitory media or memory, such assecondary or persistent long term storage, like read only memory (ROM),optical or magnetic disks, compact-disc read only memory (CD-ROM), forexample. The computer readable media may also be any other volatile ornon-volatile storage systems. The computer readable medium may beconsidered a computer readable storage medium, a tangible storagedevice, or other article of manufacture, for example.

In addition, for the method 300 and other processes and methodsdisclosed herein, each block in FIG. 3 may represent circuitry that iswired to perform the specific logical functions in the process. For thesake of example, the method 300 shown in FIG. 3 will be described asimplemented by an example computing device, such as the computing device111 in FIG. 1. The method 300 can also be described as implemented by anautonomous vehicle, as the computing device may be onboard the vehicleor may be off-board but in wireless communication with the vehicle.Therefore the terms “computing device” and “autonomous vehicle” can beinterchangeable herein. However, in some examples, the computing devicemay be configured to control the vehicle in an autonomous orsemi-autonomous operation mode. It should be understood that otherentities or combinations of entities can implement one or more steps ofthe example method 300.

At block 302, the method 300 includes identifying a first object aheadof an autonomous vehicle. Further, at block 304, the method includesidentifying a second object ahead of the first object, where the firstand second objects are in substantially in a same lane as the autonomousvehicle. It should be understood, however, that additionally oralternatively to identifying objects ahead of (or substantially in frontof) the autonomous vehicle and in substantially the same lane as theautonomous vehicle, the computing device can be configured to identifyother objects within an environment of the autonomous vehicle, includingobjects to the side of the autonomous vehicle (e.g., adjacent lanes on aroad), and/or behind the autonomous vehicle, for example.

In some examples, in addition to the first object, other objects may beidentified by the computing device between the autonomous vehicle andthe second object, such as multiple vehicles travelling in front of theautonomous vehicle and behind the second object. The objects may bewithin a longitudinal distance threshold from the autonomous vehicleand/or within a lateral distance threshold from the autonomous vehicle.For example, on a road of travel, the autonomous vehicle may adjust itsspeed based on the behavior of other vehicles or objects in front of theautonomous vehicle that are in the same lane as the vehicle. Further,the autonomous vehicle may adjust its speed based on the behavior ofvehicles or other objects in adjacent lanes on the road of travel, suchas an adjustment made when a nearby vehicle moves from its current laneto the lane in which the autonomous vehicle is travelling. In somescenarios, while it may be desirable for the autonomous vehicle toadjust its speed based on a vehicle travelling in the same lane at agiven longitudinal distance in front of the autonomous vehicle or behindthe autonomous vehicle, it may not be desirable for the autonomousvehicle to adjust its speed based on the behavior of objects at thatsame given distance laterally from the autonomous vehicle (e.g., objectsin lanes that are beyond the adjacent lanes).

In some examples, the second object ahead of the first object, as wellas other objects between the autonomous vehicle and the second object,may include another vehicle (e.g., cars, bicycles, etc.). In otherexamples, the second object may include a traffic control object, suchas a stop sign, traffic light, traffic cone, road surface marking, roadboundary barrier, and the like. In still other examples, the secondobject may be a pedestrian, such as a pedestrian crossing the street atan upcoming intersection. Other examples are also possible.

In addition to identifying the objects, the computing device may beconfigured to determine respective characteristics of each object. Forexample, the computing device may be configured to determine a type ofan object or classify the object (e.g., car or truck, car or motorcycle,traffic sign or a pedestrian, etc.). Further, the computing device candetermine whether the object is moving or stationary. In some examples,at least one object identified between the autonomous vehicle and thesecond object may be a dynamic (e.g., moving) object.

The computing device may be configured to estimate a size (e.g., widthand length) and weight of the object. Further, the computing device maybe configured to determine a direction of motion of the object, such asif the object is moving towards the autonomous vehicle or away from thevehicle. Still further, the computing device may be configured todetermine a transmission type (e.g., manual and automatic) andtransmission mode of the object, such as whether the object is in park,drive, reverse, or neutral transmission mode. Yet still further, thecomputing device may be configured to determine a position of the objectin a respective lane on the road or path of travel, and how close theobject may be to lane boundaries. In some examples, the computing devicemay be configured to determine relative longitudinal speed and lateralspeed of the object with respect to the autonomous vehicle. Thesecharacteristics are examples for illustration, and other characteristicscan be determined as well.

Characteristics of traffic control objects may also be determined, suchas a color of a traffic light. In some examples, when a red trafficlight is identified as an object substantially in front of the vehicle(e.g., the second object), the computing device may be configured toignore objects beyond the traffic light (e.g., further away from theautonomous vehicle than the traffic light). The same configuration mayapply in a scenario in which a stop sign is identified. In otherexamples, when a green traffic light is identified by the computingdevice, the computing device may be configured to ignore the greentraffic light as an object and, as such, the speed of the autonomousvehicle may not be adjusted based on the presence of the green trafficlight. In still other examples, when a yellow traffic light isidentified by the computing device, the computing device may beconfigured to perform functions as if the traffic light was red orgreen, or may perform other functions. The computing device may also beconfigured to detect when a traffic light will change colors.

To identify the object and characteristics of the objects, the computingdevice may be configured to use the sensors and devices coupled to theautonomous vehicle. For example, a camera, such as the camera 134 inFIG. 1 or the camera 210 in FIG. 2 or any other image-capture device,may be coupled to the autonomous vehicle and may be in communicationwith the computing device. The camera may be configured to captureimages or a video of the path/road of travel and vicinity of thepath/road of travel. The computing device may be configured to receivethe images or video and identify, using image processing techniques forexample, objects depicted in the image or the video. The computingdevice may be configured compare portions of the images to templates ofobjects to identify the objects, for example.

In another example, the computing device may be configured to receive,from a LIDAR device (e.g., the LIDAR unit 132 in FIG. 1) coupled to theautonomous vehicle and in communication with the computing device,LIDAR-based information that may include a three-dimensional (3D) pointcloud. The 3D point cloud may include points corresponding to lightemitted from the LIDAR device and reflected from objects on the road orin the vicinity of the road.

As described with respect to the LIDAR unit 132 in FIG. 1, operation ofthe LIDAR device may involve an optical remote sensing technology thatenables measuring properties of scattered light to find range and/orother information of a distant target. The LIDAR device, for example,may be configured to emit laser pulses as a beam, and scan the beam togenerate two dimensional or three dimensional range matrices. In anexample, the range matrices may be used to determine distance to anobject or surface by measuring time delay between transmission of apulse and detection of a respective reflected signal.

In examples, the LIDAR device may be configured to scan an environmentsurrounding the autonomous vehicle in three dimensions. In someexamples, more than one LIDAR device may be coupled to the vehicle toscan a complete 360° horizon of the vehicle. The LIDAR device may beconfigured to provide to the computing device a cloud of point datarepresenting obstacles or objects, which have been hit by the laser, onthe road and the vicinity of the road. The points may be represented bythe LIDAR device in terms of azimuth and elevation angles, in additionto range, which can be converted to (X, Y, Z) point data relative to alocal coordinate frame attached to the autonomous vehicle. Additionally,the LIDAR device may be configured to provide to the computing deviceintensity values of the light or laser reflected off the obstacles thatmay be indicative of a surface type of a given object. Based on suchinformation, the computing device may be configured to identify theobjects and characteristics of the objects such as type of the object,size, speed, whether the object is a traffic sign with a retroreflectivesurface, etc.

In still another example, the computing device may be configured toreceive, from a RADAR device (e.g., the RADAR unit 130 in FIG. 1)coupled to the autonomous vehicle and in communication with thecomputing device, RADAR-based information relating to location andcharacteristics of the objects. The RADAR device may be configured toemit radio waves and receive back the emitted radio waves that bouncedoff the surface of objects on the road and in the vicinity of the road.The received signals or RADAR-based information may be indicative, forexample, of dimensional characteristics of a given object, and mayindicate whether the given object is stationary or moving.

In yet still another example, the computing device may be configured tohave access to map information that identifies static objects that arepermanently placed on the road such as traffic lights, traffic signs,guard rails, etc. The map information may also be updated periodically,and may include information about accidents that have recently occurredand the resulting wreckage or traffic that may be in the vicinity of theautonomous vehicle.

In one example, the computing device may be configured to detect andidentify the objects and characteristics of the objects based oninformation received from multiple sources such as the image-capturedevice, the LIDAR device, the RADAR device, etc. However, in anotherexample, the computing device may be configured to identify the objectsbased on information received from a subset of the multiple sources. Forexample, images captured by the image-capture device may be blurred dueto a malfunction of the image-capture device, and in another example,details of the road may be obscured in the images because of fog. Inthese examples, the computing device may be configured to identify theobjects based on information received from the LIDAR and/or RADAR unitsand may be configured to disregard the information received from theimage-capture device.

In another example, the autonomous vehicle may be travelling in aportion of the road where some electric noise or jamming signals maycause the LIDAR device and/or RADAR device to operate incorrectly. Inthis case, the computing device may be configured to identify theobjects based on information received from the image-capture device, andmay be configured to disregard the information received from the LIDARand/or RADAR units.

In one example, the computing device may be configured to rank thesesources of information based on a condition of the road (e.g., fog,electronic jamming, etc.). The ranking may be indicative of whichdevice(s) to rely on or give more weight to in identifying the objects.As an example, if fog is present in a portion of the road, then theLIDAR and RADAR devices may be ranked higher than the image-baseddevice, and information received from the LIDAR and/or RADAR devices maybe given more weight than respective information received from theimage-capture device.

The computing device may also be configured to receive, from sensors anddevices coupled to the autonomous vehicle, information associated with,for example, condition of systems and subsystems of the autonomousvehicle. Further, the computing device may be configured to receiveinformation associated with the surrounding environment of theautonomous vehicle, such as driving conditions and road conditions(e.g., rain, snow, etc.). For example, information indicating that theroad is icy or wet ahead of the vehicle may cause the computing deviceto modify its adjustment of the autonomous vehicle's speed. Otherexamples are also possible.

At block 306, the method 300 includes determining a first bufferdistance, the first buffer distance being a minimal distance behind thefirst object at which the autonomous vehicle will substantially reach aspeed of the first object. Further, at block 308, the method includesdetermining a second buffer distance, the second buffer distance being aminimal distance behind the second object at which the first object willsubstantially reach a speed of the second object. Still further, atblock 310, the method includes determining a distance at which to adjusta speed of the autonomous vehicle based on the first and second bufferdistances and the speed of the autonomous vehicle. It should beunderstood that other buffer distances may be determined as well whenother objects are identified within an environment of the autonomousvehicle in addition to the first and second objects.

FIG. 4A illustrates an example scenario for determining the bufferdistances and the distance at which to adjust the speed of the vehicle.As shown, an autonomous vehicle 400 (e.g., a computing device of theautonomous vehicle) travelling in the +y-direction may identify aplurality of objects 402-408 substantially in front of the autonomousvehicle 400 and also travelling in the +y-direction. The plurality ofobjects 402-408 may include an object travelling ahead of the autonomousvehicle 400, such as vehicle 402, and multiple objects between theautonomous vehicle 400 and vehicle 402, such as vehicle 404, vehicle406, and vehicle 408. As shown, each vehicle may have respectivecharacteristics that can be used to determine the distance, such as arange from the vehicle to the autonomous vehicle 400, r_(i), aspeed/velocity of the car, v_(i), and an acceleration (or deceleration)of the car, a_(i).

The autonomous vehicle 400 may also have characteristics that can beused to determine the distance, such as a speed/velocity of theautonomous vehicle 400, r₀, and an acceleration/deceleration of theautonomous vehicle 400, a₀. Further, the distance may be based on alongitudinal speed of the autonomous vehicle, v_(LONG), and a lateralspeed of the autonomous vehicle, v_(LAT). In some examples, in additionto the distance being based on the speed of the autonomous vehicle(e.g., the current speed of the autonomous vehicle), the distance may befurther based on other characteristics of the vehicle, including theautonomous vehicle's direction of motion, size, position on a path oftravel, and type, among other characteristics.

In some examples, the autonomous vehicle 400 may also determine a bufferdistance for each of the vehicles 402-408 and may use each bufferdistance to predict the behavior of the vehicles 402-408 and determine adistance behind the vehicles that the autonomous vehicle 400 shouldadjust its speed. Each buffer distance may represent a minimal distancebehind a given vehicle at which another vehicle directly following thegiven vehicle will match (or substantially reach) the speed of the givenvehicle. By determining the buffer distances, the autonomous vehicle 400can determine when (or at what distance from the nearest or furthestobject) it will need to adjust its speed. For instance, the autonomousvehicle 400 may determine that vehicle 404 will match the speed ofvehicle 402 at buffer distance b₄, that vehicle 406 will match the speedof vehicle 404 at buffer distance b₃, and that vehicle 408 will matchthe speed of vehicle 406 at buffer distance b₂. Note that bufferdistance b₁ is approximately zero since vehicle 408 is closest inproximity to the autonomous vehicle 400 and thus the autonomous vehicle400 can be assumed to be matching the speed of vehicle 408. Further, ifvehicle 402 begins to slow down, the autonomous vehicle 400 maydetermine the buffer distances and thus determine that for each vehiclebetween the autonomous vehicle 400 and vehicle 402, the autonomousvehicle 400 will need to slow down earlier (at a certain distance fromvehicle 402). The autonomous vehicle 400 may then begin to slow downbefore vehicles 404-408 react to the speed change of vehicle 402 andbegin to slow down as well.

The buffer distance may be a function of the range from the vehicle tothe given vehicle, and may be shorter when the vehicle is further awayfrom the autonomous vehicle 400. For example, the buffer distance ofvehicle 402, b₄, may be shorter than the other buffer distances becausevehicle 402 is the furthest away from the autonomous vehicle 400 andthus its future behavior does not affect the autonomous vehicle 400 asmuch as the behaviors of the vehicles closer to the vehicle 400. In someexamples, the buffer distance may be determined by multiplying a giventime constant by the speed of the vehicle 400. Other examples ofdetermining buffer distances are also possible.

FIG. 4B another example scenario for determining the distance at whichto adjust the speed of the vehicle. As shown, an autonomous vehicle 450similar to the autonomous vehicle 400 of FIG. 4A that is travelling inthe +y-direction may identify a plurality of objects 452-458substantially in front of the autonomous vehicle 450. The autonomousvehicle 450 may identify a red traffic light 452 (e.g., the secondobject) at a range of r_(S) from the vehicle 450. Further, theautonomous vehicle 450 may identify vehicle 454, vehicle 456, andvehicle 458, each travelling in the +y-direction, and determinecharacteristics of each vehicle, such as respective speed (longitudinaland lateral), acceleration, range from the autonomous vehicle 450, andothers.

Upon the autonomous vehicle 450 identifying the red traffic light 452and the moving vehicles 454-458 between the autonomous vehicle 450 andthe red traffic light 452, the autonomous vehicle 450 may be configuredto determine a distance at which to adjust its speed. Further, theautonomous vehicle 450 may determine the distance before the vehicles454-458 begin to slow down and stop due to the upcoming red trafficlight ahead. In other words, the autonomous vehicle 450 may predict thatthe vehicles 454-458 will need to begin slowing down and stop before thered traffic light 452 and thus adjust its speed before the vehicles454-458 come to a stop or begin to decelerate. In some scenarios, thered traffic light 452 may instead be a stopped vehicle or other objectthat is not moving, and would be identified and treated the same way bythe autonomous vehicle 450 in such scenarios (e.g., as an objecttravelling at zero speed).

In some examples where vehicles 454-458 are not present and no objectsare between the autonomous vehicle 450 and the red traffic light 452,the autonomous vehicle 450 may determine that it needs to come to a stopover the distance r_(S). However, in examples such as the oneillustrated in FIG. 4B, the autonomous vehicle 450 may determine that ithas a shorter distance to come to a stop since vehicles 454-458 are infront of it. As such, the autonomous vehicle 450 may determine thedistance at which to adjust its speed based on the range, r_(S), and abuffer distance, b_(S).

In addition to or alternatively to the factors affecting buffer distanceas noted above, the buffer distance may be based on a length of a givenobject or objects and a predetermined minimal gap between each object atzero speed. For instance, as shown, each vehicle may have a length, y.The length of the objects may be different in other examples. Further,the predetermined (e.g., estimated) minimal gap between each vehiclewhen stopped may be a gap, x. As such, the autonomous vehicle 450 maydetermine b_(S) by adding the lengths of the vehicles to thepredetermined gaps (e.g., b_(S)=y+y+y+x+x=3y+2x). Therefore, thedistance at which the vehicle 450 should adjust its speed may equal therange to the red traffic light 452, r_(S), reduced by the bufferdistance, b_(S) (e.g., r_(S), −b_(S)).

In general, when a traffic light is identified, the autonomous vehicle(e.g., the computing device of the vehicle) may determine the distanceat which to adjust its speed based on the current state of the trafficlight. In some examples, however, the autonomous vehicle may beconfigured to predict a change in a state of the traffic light. Forinstance, the autonomous vehicle may determine that, while the trafficlight is currently red, the traffic light may change to green after agiven period of time. Depending on the given period of time, theautonomous vehicle may consider the traffic light as a green trafficlight and predict that the vehicles between the autonomous vehicle andthe traffic light will begin to increase their speed. The autonomousvehicle may then speed up, slow down, or maintain speed, depending onits current speed.

As an example, the autonomous vehicle may be approaching a red trafficlight, but may be a far enough distance away from the traffic light andstopped vehicles in front of the traffic light that it has not yet begunto slow down. The autonomous vehicle may determine that the trafficlight will change from red to green after a short period of time andthus determine that the vehicles will begin to accelerate soon. Sincethe autonomous vehicle may still be a far distance from the trafficlight and the vehicles, the autonomous vehicle may maintain its currentspeed (or increase its speed) if it determines that the vehicles willhave sped up enough by the time the autonomous vehicle gets closer tothem so that the autonomous vehicle's current speed (or increased speed)may substantially match the speed of the previously-stopped vehicleclosest to the autonomous vehicle that the autonomous vehicle isapproaching (e.g., vehicle 458 in FIG. 4B). Other examples are alsopossible.

It should be understood that the reasoning applied in the exampledescribed with respect to FIG. 4B can also apply to examples where theplurality of identified objects are moving (e.g., no traffic controldevices), such as the example described with respect to FIG. 4A. Itshould also be understood that the distances/ranges between theautonomous vehicle 450, the red traffic light 452, and the vehicles454-458 as illustrated in FIG. 4B may not be to scale. Specifically, itis likely that the distance between vehicle 454 and the red trafficlight 452 would be much greater than the minimal gap distance betweenvehicles, x.

Referring back to FIG. 3, at block 312, the method 300 includesproviding instructions to adjust the speed of the autonomous vehiclebased on the distance. In some examples where multiple dynamic objectsare between the autonomous vehicle and the second object, the computingdevice may adjust the speed of the autonomous vehicle prior todetermining a change of the speed of one or more of the dynamic objects.

The control system of the autonomous vehicle may comprise multiplecontrol strategies that may be predetermined or adaptive to changes in adriving environment of the autonomous vehicle, the driving environmentincluding the predicted actions of objects substantially in front of theautonomous vehicle, behind the autonomous vehicle, and/or to the side ofthe autonomous vehicle. Generally, a control strategy may comprise setsof instructions or rules associated with traffic interaction in variousdriving contexts. The control strategy, for example, may comprise rulesthat determine a speed of the autonomous vehicle, steering angle, and alane that the autonomous vehicle may travel on while taking into accountsafety and traffic rules and concerns (e.g., other vehicles stopped atan intersection and windows-of-opportunity in yield situation, lanetracking, speed control, distance from other vehicles on the road,passing other vehicles, and queuing in stop-and-go traffic, and avoidingareas that may result in unsafe behavior such as oncoming-traffic lanes,etc.). For instance, the computing device may be configured todetermine, based on the distance determined at block 310, a controlstrategy comprising rules for actions that control speed, steeringangle, and lane of the autonomous vehicle. The control strategy may alsobe further based on a lateral distance between the autonomous vehicleand nearby objects (e.g., road boundaries and vehicles travelling inadjacent lanes). Further, a given control strategy (or multiplestrategies) may comprise a program or computer instructions thatcharacterize actuators controlling the autonomous vehicle (e.g.,throttle, steering gear, brake, accelerator, or transmission shifter).

In some examples, the instructions provided by the computing device toadjust the control of the autonomous vehicle (e.g., speed, steering,etc.) may be based on road geometry, such as if the road is straight,curving slightly, curving sharply, etc.

FIG. 5 illustrates an implementation of the example method on a road oftravel. The vehicle 500 may be in a lane 501 on a road such as ahighway. The computing device configured to control the autonomousvehicle 500 may be configured to identify a plurality of objectssubstantially in front of the autonomous vehicle 500 on the road oftravel. The plurality of objects may include an object 502, such as amoving object (e.g., cars, trucks, etc.), that is in the same lane 501as the autonomous vehicle 500. The plurality of objects may also includemoving objects 504, 506, 508, and 510 that are in an adjacent lane 511to the lane 501 of the autonomous vehicle 500. In some examples, thecomputing device may not be configured to identify object 510 until theentirety of the length of the object 510 is in front of the autonomousvehicle 500.

In some examples, the computing device may be configured to identifyother objects within the environment of the autonomous vehicle 500, suchas object 512 located behind the autonomous vehicle 500 in an adjacentlane. In other examples, the computing device may be configured toignore objects, such as object 514, that may be beyond a thresholddistance from the autonomous vehicle 500. The computing device may alsoidentify static objects such as a guard rail 516. The computing devicefurther may be configured to determine characteristics of the objects502-516, such as size, location, speed, etc.

In some examples, the autonomous vehicle 500 may be configured to onlyidentify objects substantially in front of it, and may thus ignoreobjects 512 and 514. In other examples, the computing device may beconfigured to identify objects 512 and 514, but may ignore them untilthey are within a threshold distance from the autonomous vehicle 500. Insuch examples, the computing device may monitor characteristics ofobjects 512 and 514 so as to predict their future behavior while not yettaking their characteristics into account in determining the distance atwhich to adjust the speed of the autonomous vehicle 500 until theobjects are within the threshold distance from the autonomous vehicle500. For instance, the autonomous vehicle 500 may predict that object512 will accelerate, exceed the speed of the autonomous vehicle 500, andpass the autonomous vehicle 500. The autonomous vehicle 500 may predictother actions of the object 512 as well (e.g., object 512 may pass theautonomous vehicle and move into the same lane as the autonomousvehicle).

The computing device may determine the distance at which to adjust thespeed of the autonomous vehicle 500 based on identified objects 502-516,their characteristics, and respective buffer distances. In someexamples, however, the computing device may determine that one or moreobjects substantially in front of the autonomous vehicle 500, such asobject 508, may change lanes or are in the process of changing lanes. Assuch, the computing device may modify the distance to account for this(e.g., adjust the buffer distances). For instance, if object 508 changeslanes from lane 511 to lane 501, object 508 may be closer in proximityto the autonomous vehicle 500 and thus the autonomous vehicle 500 mayneed to adjust its speed in order to match the speed of object 508.Prior to detecting that object 508 is changing lanes, the autonomousvehicle 500 may have been travelling at a higher speed since no objectswere identified to be in the same lane 501 as the autonomous vehicle 500and object 502, and after detecting that object 508 has changed lanes,the autonomous vehicle 500 may reduce its speed. Further, the computingdevice may predict that object 510 will speed up to match the speed ofobject 506 once object 508 has fully or partially entered lane 501. Thecomputing device may be configured to make otherdeterminations/predictions as well, and modify the distance accordingly.

In some examples, the computing device may be configured to prioritizeamongst the identified objects 502-516 in order to determine thedistance. For instance, if object 508 is in the same lane 501 as theautonomous vehicle 500 and object 502, the behavior of object 508 may betaken more into account than the behaviors of objects 504, 506, and 510,which are in the adjacent lane 511. Such prioritization may take theform of modified buffer distances, for example (e.g., the bufferdistance of object 510 may be shorter than the buffer distance of object508, despite object 510 being closer in proximity to the autonomousvehicle 500). Thus, the computing device may be configured to add orsubtract a buffer amount of distance to the determined distance toaccount for or compensate for such lane changes, as well as for anyother changes in the environment of the autonomous vehicle 500. Theprioritization may be implemented in other ways as well.

In some examples, the method described above may only be implemented bythe computing device when there is at least one moving object betweenthe autonomous vehicle and the second object, in addition to theidentified first object. In examples where there are no moving objectsbetween the autonomous vehicle and the second object, the methoddescribed above may not be implemented, or may be implemented inaccordance with another method or methods not described herein.

In some embodiments, the disclosed methods may be implemented ascomputer program instructions encoded on a computer-readable storagemedia in a machine-readable format, or on other non-transitory media orarticles of manufacture. FIG. 6 is a schematic illustrating a conceptualpartial view of an example computer program product 600 that includes acomputer program for executing a computer process on a computing device,arranged according to at least some embodiments presented herein. In oneembodiment, the example computer program product 600 is provided using asignal bearing medium 601. The signal bearing medium 601 may include oneor more program instructions 602 that, when executed by one or moreprocessors (e.g., processor 113 in the computing device 111) may providefunctionality or portions of the functionality described above withrespect to FIGS. 1-5. Thus, for example, referring to the embodimentsshown in FIG. 3, one or more features of blocks 302-306 may beundertaken by one or more instructions associated with the signalbearing medium 601. In addition, the program instructions 602 in FIG. 6describe example instructions as well.

In some examples, the signal bearing medium 601 may encompass acomputer-readable medium 603, such as, but not limited to, a hard diskdrive, a Compact Disc (CD), a Digital Video Disk (DVD), a digital tape,memory, etc. In some implementations, the signal bearing medium 601 mayencompass a computer recordable medium 604, such as, but not limited to,memory, read/write (R/W) CDs, R/W DVDs, etc. In some implementations,the signal bearing medium 601 may encompass a communications medium 605,such as, but not limited to, a digital and/or an analog communicationmedium (e.g., a fiber optic cable, a waveguide, a wired communicationslink, a wireless communication link, etc.). Thus, for example, thesignal bearing medium 601 may be conveyed by a wireless form of thecommunications medium 605 (e.g., a wireless communications mediumconforming to the IEEE 802.11 standard or other transmission protocol).

The one or more programming instructions 602 may be, for example,computer executable and/or logic implemented instructions. In someexamples, a computing device such as the computing device described withrespect to FIGS. 1-5 may be configured to provide various operations,functions, or actions in response to the programming instructions 602conveyed to the computing device by one or more of the computer readablemedium 603, the computer recordable medium 604, and/or thecommunications medium 605. It should be understood that arrangementsdescribed herein are for purposes of example only. As such, thoseskilled in the art will appreciate that other arrangements and otherelements (e.g. machines, interfaces, functions, orders, and groupings offunctions, etc.) can be used instead, and some elements may be omittedaltogether according to the desired results. Further, many of theelements that are described are functional entities that may beimplemented as discrete or distributed components or in conjunction withother components, in any suitable combination and location.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.The various aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting, with the true scopebeing indicated by the following claims, along with the full scope ofequivalents to which such claims are entitled. It is also to beunderstood that the terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to belimiting.

What is claimed is:
 1. A method comprising: identifying a first vehicletravelling ahead of an autonomous vehicle; identifying a second vehicleahead of the first vehicle, the first and second vehicles travelling insubstantially a same lane as the autonomous vehicle; determining a firstbuffer distance, the first buffer distance being a minimal distancebehind the first vehicle at which the autonomous vehicle willsubstantially reach a speed of the first vehicle; determining a secondbuffer distance, the second buffer distance being a minimal distancebehind the second vehicle at which the first vehicle will substantiallyreach a speed of the second vehicle; determining a distance at which toadjust a speed of the autonomous vehicle based on the first and secondbuffer distances and the speed of the autonomous vehicle; and providinginstructions by a computing device to adjust the speed of the autonomousvehicle based on the distance.
 2. The method of claim 1, whereinproviding the instructions by the computing device to adjust the speedof the autonomous vehicle comprises providing the instructions to adjustthe speed of the autonomous vehicle prior to determining a change of thespeed of at least one of the first and second vehicles.
 3. The method ofclaim 1, further comprising: receiving, from an image-capture devicecoupled to the autonomous vehicle, an image; and wherein identifying thefirst and second vehicles comprises identifying at least one of thefirst and second vehicles in the image.
 4. The method of claim 1,wherein the first and second vehicles are within a longitudinal distancethreshold from the autonomous vehicle and within a lateral distancethreshold from the autonomous vehicle.
 5. The method of claim 1, whereinthe speed of the first and second vehicles includes one or more of alongitudinal speed of the first and second vehicles and a lateral speedof the first and second vehicles, and wherein the distance at which toadjust the speed of the autonomous vehicle is further based oncharacteristics of the first and second vehicles, the characteristicsincluding one or more of: an acceleration of a vehicle of the first andsecond vehicles, a deceleration of the vehicle, whether the vehicle ismoving or stationary, a direction of motion of the vehicle, a size ofthe vehicle, a weight of the vehicle, a position of the vehicle on aroad of travel, and a type of the vehicle.
 6. The method of claim 1,wherein the distance at which to adjust the speed of the autonomousvehicle is further based on characteristics of the autonomous vehicle,the characteristics including one or more of: an acceleration of theautonomous vehicle, a deceleration of the autonomous vehicle, adirection of motion of the autonomous vehicle, a size of the autonomousvehicle, a position of the autonomous vehicle on a road of travel, and atype of the autonomous vehicle.
 7. The method of claim 1, furthercomprising: identifying an object ahead of the second vehicle, whereinthe object includes another vehicle or a traffic control object; anddetermining a third buffer distance, the third buffer distance being aminimal distance behind the object at which the second vehicle willsubstantially reach a speed of the object, wherein the distance at whichto adjust the speed of the autonomous vehicle is further based on thethird buffer distance.
 8. A non-transitory computer readable mediumhaving stored thereon instructions that, upon execution by a computingdevice, cause the computing device to perform functions comprising:identifying a first vehicle travelling ahead of an autonomous vehicle;identifying a second vehicle ahead of the first vehicle, the first andsecond vehicles travelling in substantially a same lane as theautonomous vehicle; determining a first buffer distance, the firstbuffer distance being a minimal distance behind the first vehicle atwhich the autonomous vehicle will substantially reach a speed of thefirst vehicle; determining a second buffer distance, the second bufferdistance being a minimal distance behind the second vehicle at which thefirst vehicle will substantially reach a speed of the second vehicle;determining a distance at which to adjust a speed of the autonomousvehicle based on the first and second buffer distances and the speed ofthe autonomous vehicle; and providing instructions to adjust the speedof the autonomous vehicle based on the distance.
 9. The non-transitorycomputer readable medium of claim 8, wherein providing the instructionsto adjust the speed of the autonomous vehicle comprises providing theinstructions to adjust the speed of the autonomous vehicle prior todetermining a change of the speed of at least one of the first andsecond vehicles.
 10. The non-transitory computer readable medium ofclaim 8, wherein the first and second buffer distances are further basedon lengths of the first and second vehicles and a predetermined minimalgap between the first and second vehicles at zero speed.
 11. Thenon-transitory computer readable medium of claim 8, wherein the distanceat which to adjust the speed of the autonomous vehicle is based in parton a time constant multiplied by the speed of the autonomous vehicle.12. A system comprising: at least one processor; and a memory havingstored thereon instructions that, upon execution by the at least oneprocessor, cause the system to perform functions comprising: identifyinga first object ahead of an autonomous vehicle; identifying a secondobject ahead of the first object, wherein the first and second objectsare in substantially a same lane as the autonomous vehicle; determininga first buffer distance, the first buffer distance being a minimaldistance behind the first object at which the autonomous vehicle willsubstantially reach a speed of the first object; determining a secondbuffer distance, the second buffer distance being a minimal distancebehind the second object at which the first object will substantiallyreach a speed of the second object; determining a distance at which toadjust a speed of the autonomous vehicle based on the first and secondbuffer distances and the speed of the autonomous vehicle; and providinginstructions to adjust the speed of the autonomous vehicle based on thedistance.
 13. The system of claim 12, wherein providing the instructionsto adjust the speed of the autonomous vehicle comprises providing theinstructions to adjust the speed of the autonomous vehicle prior todetermining a change of the speed of at least one of the first andsecond objects.
 14. The system of claim 13, wherein the change of thespeed of at least one of the first and second objects includes anincrease of the speed of the first object, and wherein the instructionsto adjust the speed of the autonomous vehicle include instructions toincrease the speed of the autonomous vehicle so as to substantiallyreach the increased speed of the first object.
 15. The system of claim13, wherein the change of the speed of at least one of the first andsecond objects includes a decrease of the speed of the first object, andwherein the instructions to adjust the speed of the autonomous vehicleinclude instructions to decrease the speed of the autonomous vehicle soas to substantially reach the decreased speed of the first object. 16.The system of claim 12, wherein the second object includes one or moreof a stop sign, a traffic light, a traffic cone, a road surface marking,and a road boundary barrier.
 17. The system of claim 12, wherein atleast one of the first and second objects includes a vehicle travellingahead of the autonomous vehicle.
 18. The system of claim 12, whereindetermining the distance at which to adjust the speed of the autonomousvehicle comprises reducing a distance from the autonomous vehicle to thesecond object by the first and second buffer distances.
 19. The systemof claim 12, wherein the distance at which to adjust the speed of theautonomous vehicle is further based on characteristics of the first andsecond objects, the characteristics including one or more of: alongitudinal speed of an object of the first and second objects, alateral speed of the object, an acceleration of the object, adeceleration of the object, a direction of motion of the object, a sizeof the object, a weight of the object, a position of the object on aroad of travel, and a type of the object.
 20. The system of claim 19,further comprising: a light detection and ranging (LIDAR) device coupledto the autonomous vehicle, wherein the LIDAR device is configured toprovide LIDAR-based information comprising a three-dimensional (3D)point cloud that includes a set of points based on light emitted fromthe LIDAR device and reflected from the first and second objects; acamera coupled to the autonomous vehicle, wherein the camera isconfigured to provide one or more images of the first and secondobjects; and a radio detection and ranging (RADAR) device coupled to theautonomous vehicle, wherein the RADAR device is configured to provideRADAR-based information relating to at least one of the characteristicsof the first and second objects.